Couple of random thoughts of how I ended up where I have.... (I reserve the right to change my mind! :p)
-I started with a GoLite Poncho Tarp and no bivy. I tended to only go backpacking when the weather was good and when it did rain is was light. I ~still~ sh_t myself worrying about my down bag those night as I was sleeping under a postage stamp and I got VERY lucky that my bag did not get wet. As I got more serious I realized my shelter protection was severely lacking and hiking in the NE with rock scrambles, roots, and places where I had to see my feet on the trail, the Poncho wasn't cutting it either.
-I've never liked bivies. I found them expensive, heavy (unless you go with .33 SULUK bivy, then I would cry the day I put a hole in it w/ no groundsheet), read about condensation problems (though I admit, never tried one). They do however prevent drafts so your sleeping bag is warmer, but I'd rather just pitch the tarp three sides to the ground to stop the wind.
-I bought the BearPaw Cub Den 1.5 because it was inexpensive as compared to the Hexamid, it had bonded seams, was larger (I really thought the Hexamid would not cover me for gusty rain in the NE w/out the extended beak...then u give back most of the weight advantage) and could be delivered quicker. I also liked that it had permiter netting as opposed to netting underneath that I feared would wear out over time. The Cub Den 1.5 gives great coverage but at a price...it takes up a lot of real estate to pitch with all those guy lines going everywhere. I also didn't like the fact that I have to carry the permiter netting even in the Fall when I don't need bug protection. And while the Cub Den 1.5 is holding up fine, the bonding is certainly more complicated on/near stress points.
-I started to evaluate CF shelters/Tarps that I did not have to carry bug protection 24/7. I settled on a 9x7 tarp for a few reasons:
1) smallest tarp (least weight) while not needing bivy
2) Flexible pitches to use natural wind breaks
3) Need less real estate to pitch that Cub Den 1.5
4) Can pitch bug shelter alone in AT Shelter if I want
5) Total system weighs less
6) Can pee out the side in the middle of the night. :p
7) Costs less
8) Less complex construction (more durable?)
9) Can more fully utilize Bag liner (trash compactor/nylofume bag) as lower leg bivy while dropping weight elsewhere (the tarp itself :p)
My comparison spreadsheet:
Here I am in my Cub Den 1.5, you can see the trash compactor bag on my legs to prevent spray that was coming in on the side/opening through the mesh (It was calm when we went to bed, if I knew the heavens would open up, I would of pitched lower). I now use the same technique w/ my tarp. My legs are at the OPEN end of my a-frame when I pitch three sides to the ground. The nylofume/trash compacor bag takes care of spray from the open end.
(BPL member, Roleigh Martin's Hexamid Twin is the "green thing" :p)